To make use of mobile network resource effectively, 3GPP (Third Generation Partnership Project) has proposed MBMS, that is, a point-to-multipoint service in which a data source sends data to a plurality of users is provide, to realize shared network resource and increase the utilization of network resource, especially that of precious air interface resources. MBMS not only enables to achieve multicast and broadcast of message type of pure text with low rate, but also to achieve multicast and broadcast of high speed multimedia services, providing a wide variety of services of video, audio and multimedia, which undoubtedly conforms to the trend of the future development of mobile data and provides a better service prospect for the development of mobile communication.
FIG. 1 shows the structure model diagram of MBMS service system. As shown in FIG. 1, Broadcast-Multicast Service Center (BM-SC) is a new mobile network functional entity for authorizing and initiating of MBMS carried services in the mobile network and transmitting MBMS contents according to the predetermined schedule as an entrance of contents provider.
For the existing WCDMA packet network functional entities, MBMS related functions and processes also need to be added in GGSN (General Packet Radio Service Gateway Support Node), SGSN (Serving General Packet Radio Service Support Node), RAN (Radio Access Net) and UE (User Equipment).
MBMS includes Broadcast Service and Multicast Service. There are certain scope restrictions of sending MBMS services, i.e. each MBMS service is sent within a certain area, which is called service area corresponding to a MBMS service. According to 3GPP protocol, the sending area of broadcast services is defined to be Broadcast Service area of the service and that of multicast service is defined to be Multicast service area of the service. Considering regional characteristics of some MBMS services, such as weather forecast, traffic and road condition, the content sent by it is associated with the region where UE is located. The UE, when it is located in a certain region of a MBMS service area, only needs to receive the contents associated with that region, which leads to the need of sending different service contents for the same MBMS service in different regions. Therefore, 3GPP also defines Local Broadcast Area and Local Multicast Area respectively for broadcast services and multicast services.
FIG. 2 is a diagram schematically showing the relations between MBMS service area and local service area in the prior arts. As shown in FIG. 2, for each MBMS broadcast service there is a broadcast service area, which comprises one or more local broadcast areas. In one local broadcast area, only service contents associated with this region are sent and service contents sent in different local broadcast areas may be different. For each MBMS multicast service, there is a multicast service area, which comprises one or more local multicast areas. In one local multicast area, only service contents associated with this region are sent and service contents sent in different local multicast areas may be different.
MBMS service data is sent via MBMS carrying. MBMS carrying is managed through MBMS session, one MBMS session corresponds to one MBMS carrying and each MBMS session corresponds to a MBMS Service Area (MBMS SA), which composed of one or more MBMS Service Area Identities (MBMS SA ID). Each MBMS SA ID corresponds to one or more cells in RNC (Radio Network Controller). At the beginning of a MBMS session, MBMS SA is brought to RNC by MB-SC through GGSN and SGSN, and after receiving MBMS session start request, RNC only provides MBMS services in the cells included in the service area of the MBMS services.
If one MBMS service is divided into a plurality of local areas, it is required that MBMS carryings carrying service data are different as service contents sent in different areas are not the same, and therefore, each MBMS session will be set up for each local area by BM-SC, i.e. a plurality of parallel MBMS sessions are initiated and the parallel MBMS sessions use the same TMGI (Temporary Mobile Group Identity) to indicate that they belong to the same MBMS service. As MBMS service contents sent in the same local area are required to be the same, MBMS SAs corresponding to parallel MBMS sessions in different local areas of the same MBMS service are different, in other words, cells included in the MBMS SA corresponding to MBMS sessions in different local areas of the same MBMS service cannot intersect, otherwise in the intersecting cells UE may receive service contents of a plurality of local areas.
FIG. 3 is a work flowchart showing the start-up process of an Iu interface MBMS session of 3GPP in the prior arts. As shown in FIG. 3, the process comprises the following steps:
Step 302, SGSN sends a “MBMS session start” message, which comprises the MBMS service area, to RNC to request it to inform UE MBMS of the session start-up in the service area corresponding to the MBMS service;
Step 304, RNC receives the “MBMS session start” message and detects whether there are other established sessions of the same MBMS service between this RNC and this SGSN;
Step 306, if there are other established sessions and the MBMS service area corresponding to the other established sessions and that carried by the new message sent by the SGSN intersect, the MBMS service area in the message is considered to be invalid and a “MBMS session start failure” message is returned to SGSN; and
Step 308, if there are no other established sessions of the same MBMS service or the MBMS service area corresponding to the other established sessions and that carried by the new message sent by the SGSN do not intersect, the processing is performed as a normal message and a “MBMS session start response” message or “MBMS session start failure” message is returned to SGSN according to the processing result.
The following process is performed to detect whether the MBMS service area of the MBMS session to be established and that of the other established sessions of the same service intersect or not according to the existing protocols: it is determined whether the MBMS service area carried by the MBMS session start message and that of the other established sessions have at least one or more identical MBMS service area identifications.
As one MBMS service area identification corresponds to one or more cells in RNC, one cell in RNC can be also mapped onto a plurality of MBMS service area identifications. According to the MBMS overlapping detecting method in the existing protocols, even MBMS service areas of two parallel MBMS sessions have completely different MBMS service area identifications, and the cells corresponding to respective MBMS service area identification may also overlap. Therefore, the detecting method in the existing protocols is not exact enough, which leads to that UE of the cell in the overlapping area in RNC receives plural sets of service content of the same MBMS service.
Additionally, for the parallel MBMS session start process of the same MBMS service, in the existing protocols, only MBMS service area of parallel MBMS session established between RNC and the same SGSN is detected, however, MBMS service area of parallel MBMS session established between RNC and a different SGSN is not detected. Thereby MBMS service areas of parallel session of the same MBMS service from different SGSNs may overlap, which leads to that UE of the cell in the overlapping area in RNC receives plural sets of service content of an identical MBMS service.
Therefore, a technical solution to settle the problems in the prior arts is in urgent need.